Evolution of a radio access scheme and a radio network of a cellular mobile communication (hereinafter, referred to as “Long Term Evolution (LTE®)) ” or “Evolved Universal Terrestrial Radio access (EUTRA)”) has been standardized in a 3rd Generation Partnership Project (3GPP®). In LTE, Orthogonal Frequency Division Multiplexing (OFDM) scheme, which is multicarrier transmission, is adopted as a communication scheme of wireless communication from a base station apparatus to a mobile station apparatus (referred to as downlink (DL)). Further, in LTE, Single-Carrier Frequency Division Multiple Access (SC-FDMA) scheme, which is single carrier transmission, is adopted as a communication scheme of wireless communication from the mobile station apparatus to the base station apparatus (referred to as uplink (UL)). In LTE, Discrete Fourier Transform-Spread OFDM (DFT-Spread OFDM) scheme is adopted as the SC-FDMA scheme.
LTE is developed, and thus Long Term Evolution-Advanced (LTE-A) adopting a new technology is specified. In LTE-A, at least the same channel structure as that of LTE is supported. A channel means a medium to be used in transmission of signals. A channel to be used in a physical layer is termed a physical channel, whereas a channel to be used in a Medium Access Control (MAC) layer is termed a logical channel. The types of the physical channel includes a Physical Downlink Shared CHannel (PDSCH) to be used in transmission and reception of data and control information of the downlink, a Physical Downlink Control CHannel (PDCCH) to be used in transmission and reception of control information of the downlink, a Physical Uplink Shared CHannel (PUSCH) to be used in transmission and reception of data and control information of the uplink, a Physical Uplink Control CHannel (PUCCH) to be used in transmission and reception of control information of the uplink, a Synchronization CHannel (SCH) to be used for synchronization establishment of the downlink, a Physical Random Access CHannel (PRACH) to be used for synchronization establishment of the uplink, a Physical Broadcast CHannel (PBCH) to be used in transmission of system information of the downlink, and the like. The mobile station apparatus or the base station apparatus maps and transmits signals which are generated from control information, data, and the like on each physical channel. Data which is transmitted on the physical downlink shared channel or the physical uplink shared channel is termed a transport block.
Control information which is mapped on the physical uplink control channel is termed Uplink Control Information (UCI). The uplink control information is control information (reception confirmation acknowledgement; ACK/NACK) indicating acknowledgement (ACK) or negative acknowledgement (NACK) with respect to data mapped on the received physical downlink shared channel, control information (Scheduling Request: SR) indicating a request for allocation of an uplink resource, or control information (Channel Quality Indicator: CQI) indicating reception quality (also referred to as channel quality) of the downlink.
<Cooperative Communication>
In order to reduce or suppress interference for the mobile station apparatus in a cell edge region or to increase reception signal power, applying Cooperative Multipoint communication (CoMP communication) to LTE and LTE-A is being considered which performs communication between neighboring cells in cooperation with each other. In addition, for example, the form in which the base station apparatus performs communication by using a certain frequency band will be referred to as “a cell”. For example, as the CoMP communication, in a plurality of cells, a different weighting signal process (pre-coding process) is applied on a signal, a plurality of base station apparatuses cooperate to transmit the signal to the same mobile station apparatus (also referred to as Joint Processing or Joint Transmission). This method enables to improve a signal power-to-interference noise power ratio of the mobile station apparatus and improve the reception characteristics of the mobile station apparatus. For example, as CoMP communication, a method in which a plurality of cells cooperate to perform a scheduling for the mobile station apparatus (Coordinated Scheduling: CS) is being considered. This method enables to improve a signal power-to-interference noise power ratio of the mobile station apparatus. For example, as the CoMP communication, a method in which a plurality of cells cooperate to apply a beamforming on signals and transmit the signals to the mobile station apparatus (Coordinated Beamforming: CB) is being considered. This method enables to improve a signal power-to-interference noise power ratio of the mobile station apparatus. For example, as the CoMP communication, a method in which only one cell transmits signals by using a predetermined resource, other cells do not transmit signals on a predetermined resource (Blanking and Muting) is being considered. This method enables to improve a signal power-to-interference noise power ratio of the mobile station apparatus.
In addition, with respect to a plurality of cells to be used in the cooperative communication, different cells may be configured with different base station apparatuses, different cells may be configured with different Remote Radio Heads (RRH) (more compact outdoor radio unit than the base station apparatus, and also referred to as a Remote Radio Unit: RRU) which are managed by the same base station apparatus, different cells may be configured with a base station apparatus and RRH managed by the base station apparatus, or different cells may be configured with the base station apparatus and the RRH managed by a base station apparatus different from the base station apparatus.
A base station apparatus having a wide coverage is generally referred to as a macro base station apparatus. A base station apparatus having a narrow coverage is generally referred to as a pico base station apparatus or a femto base station apparatus. The RRH is considered generally to operate in an area having a narrower coverage than that of the macro base station apparatus. The deployment of a communication system configured with the macro base station apparatus and the RRH in which the coverage supported by the macro base station apparatus includes all or a part of the coverage supported by the RRH is referred to as a heterogeneous network deployment. In a communication system of such a heterogeneous network deployment, a method is considered in which the macro base station apparatus and the RRH cooperate to transmit signals to the mobile station apparatus located within an overlapped coverage. Here, the RRH is managed by the macro base station apparatus and transmission and reception thereof are controlled. In addition, the macro base station apparatus and the RRH are connected to each other by a wired line such as an optical fiber or a wireless line using a relay technology. In this manner, since the macro base station apparatus and the RRH perform cooperative communication each using all or partially the same radio resource, it is possible to improve overall frequency utilization efficiency (transmission capacity) within an area of a coverage which has built by the macro base station apparatus.
When a mobile station apparatus is located in the vicinity of the macro base station apparatus or the RRH, the mobile station apparatus can perform single cell communication with the macro base station apparatus or the RRH. In other words, some mobile station apparatuses perform communication with the macro base station apparatus or the RRH without using the cooperative communication so as to transmit and receive signals. For example, the macro base station apparatus receives an uplink signal from the mobile station apparatus located close to the macro station apparatus in distance. For example, the RRH receives an uplink signal from the mobile station apparatus located close to the RRH in distance. Further, when the mobile station apparatus is located in the vicinity of the edge (cell edge) of a coverage built by the RRH, measures against the co-channel interference from the macro base station apparatus is required. A method has been considered which reduces or suppresses interference for the mobile station apparatus in the cell edge region by using a CoMP scheme in which neighboring base stations cooperate with each other as a multi-cell communication (cooperative communication) between the macro base station apparatus and the RRH.
Further, it has been considered that the mobile station apparatus receives signals transmitted from both the macro base station apparatus and the RRH by using cooperative communication in the downlink, and transmits signals in a form suitable for either the macro base station apparatus or the RRH in the uplink. For example, the mobile station apparatus transmits uplink signals in transmission power that is suitable for the macro base station apparatus to receive the signals. For example, the mobile station apparatus transmits uplink signals in transmission power that is suitable for the RRH to receive the signals. This reduces unnecessary interference in the uplink, and improves the frequency utilization efficiency.
It is necessary for the mobile station apparatus to obtain control information indicating a modulation scheme, a coding rate, a spatial multiplexing number, a transmission power adjustment value, allocation of resource, and the like which are used in data signals, with respect to a reception process of the data signals. With respect to LTE and LTE-A, it has been considered to introduce a new control channel (enhanced physical downlink control channel: ePDCCH) for transmitting control information regarding the data signals (NPL 1). For example, it has been considered to improve the capacities of all control channels. For example, it has been considered to support interference coordination in a frequency domain for the enhanced physical downlink control channel. For example, it has been considered to support spatial multiplexing for the enhanced physical downlink control channel. For example, it has been considered to support beamforming for the enhanced physical downlink control channel. For example, it has been considered to support diversity for the enhanced physical downlink control channel. For example, it has been considered to use the enhanced physical downlink control channel in a new type of carrier. For example, it has been considered not to perform transmission of the reference signal which is common to all mobile station apparatuses within a cell, in the new type of carrier. For example, it has been considered to further reduce the transmission frequency of the reference signal which is common to all mobile station apparatuses within the cell than the conventional transmission frequency, in the new type of carrier. For example, it has been considered to demodulate signals such as control information by using a reference signal specific to the mobile station apparatus, in the new type of carrier.
For example, as an application of beamforming, it has been considered to apply cooperative communication, and transmission through a plurality of antennas to the enhanced physical downlink control channel. Specifically, it has been considered that a plurality of base station apparatuses and a plurality of RRHs apply a pre-coding process on signals of the enhanced physical downlink control channel and apply the same pre-coding process on a reference signal (RS) for demodulating the signals of the enhanced physical downlink control channel. Specifically, it has been considered that a plurality of base station apparatuses and a plurality of RRHs allocate the enhanced physical downlink control channel and RS, to which the same pre-coding process is applied, in a region of resources in which the PDSCH is allocated, and transmit the enhanced physical downlink control channel and RS. It has been considered that a mobile station apparatus demodulates the signals of the enhanced physical downlink control channel which is subjected to the same pre-coding process, by using the received RS which has been subjected to the pre-coding process, so as to obtain control information. In this method, it is not necessary for the base station apparatus and the mobile station apparatus to exchange information regarding the pre-coding process which is applied to the signal of the enhanced physical downlink control channel.
For example, a method has been considered which configures signals of the enhanced physical downlink control channel by using resources separated in the frequency domain so as to achieve an effect of frequency diversity, as the application of diversity. In contrast, a method has been considered which configures signals of the enhanced physical downlink control channel by using the resources which are not separated in the frequency domain, when beamforming is applied to the enhanced physical downlink control channel.
A mapping method for resources configuring the enhanced physical downlink control channel has been considered. It has been considered to make the unit of resources configuring one enhanced physical downlink control channel to be a set of physical resource block pairs of a predetermined number (NPL 2). For example, the set of a plurality of physical resource block pairs which is the unit of resources configuring one enhanced physical downlink control channel is referred to as an enhanced physical downlink control channel set (ePDCCH set). In NPL 2, it is considered to configure a plurality of enhanced physical downlink control channels which are configured with the physical resource block pairs of a predetermined number, for the mobile station apparatus. For example, it is considered that in a plurality of mobile station apparatuses for which a plurality of enhanced physical downlink control channel sets are configured, some enhanced physical downlink control channel sets are configured with a plurality of common physical resource block pairs and some different enhanced physical downlink control channel sets are configured with a plurality of different physical resource block pairs. It is considered that the mobile station apparatus performs a decoding process for detecting the enhanced physical downlink control channel, in each of the plurality of configured enhanced physical downlink control channel sets.
Meanwhile, a method is considered which allocates resources of a physical uplink control channel which are used in transmission and reception of ACK/NACK for the physical downlink shared channel to which resources are allocated by downlink control information which is transmitted and received in an enhanced physical downlink control channel (NPL 3). A method is considered in which the resources of the physical uplink control channel are implicitly determined based on a logical resource (enhanced Control Channel Element: eCCE) number that is used in the enhanced physical downlink control channel, without using signaling which explicitly indicates the resources of the physical uplink control channel.
In NPL 3, with respect to resources of the physical uplink control channel which are used in transmission and reception of ACK/NACK for the physical downlink shared channel to which resources are allocated by downlink control information which is transmitted and received in the existing physical downlink control channel, and with respect to resources of the physical uplink control channel which are used in transmission and reception of ACK/NACK for the physical downlink shared channel to which resources are allocated by downlink control information which is transmitted and received in the enhanced physical downlink control channel, a method of allowing at least some resources to be shared is considered. In the existing physical downlink control channel, the method is considered in which the resources of the physical uplink control channel are implicitly determined based on the logical resource (Control Channel Element: CCE) number that is used in the physical downlink control channel, without using signaling which explicitly indicates the resources of the physical uplink control channel, the resource of the physical uplink control channel in which the association with the control channel element is started, in other words, the resource of the physical uplink control channel in which the association with the control channel element of the minimum number is performed is controlled, and the mobile station apparatus is notified, in advance, of information indicating the resource of the physical uplink control channel in which the association with the control channel element is started, from the base station apparatus. It is considered that in the enhanced physical downlink control channel, the resource of the physical uplink control channel in which association with the enhanced control channel element of the enhanced physical downlink control channel is started is controlled independently of the resource of the physical uplink control channel in which the association with the control channel element of the existing physical downlink control channel is started, and the mobile station apparatus is notified, in advance, of information indicating the resource of the physical uplink control channel in which the association with the enhanced control channel element is started, from the base station apparatus independently of the information indicating the resource of the physical uplink control channel in which the association with the control channel element is started.
In the above method in which the resource of the physical uplink control channel is implicitly determined, the resources of a plurality of physical uplink control channels are reserved in advance for the uplink. Among a plurality of resources which are reserved, the resources which are actually used in transmission and reception of uplink control information for each subframe are dependent on the control channel element of the physical downlink control channel which is used for each subframe and the enhanced control channel element of the enhanced physical downlink control channel.